feat(viral-video): 文案视频时长改为15-30秒滚轮picker

- 新增通用 DurationWheelPicker 组件（scroll-snap 原生滚动，无额外依赖）
  * 浅色紫主题：选中行 #7c3aed 紫字加粗+#f5f0ff 浅紫背景条+上下分隔线
  * 支持上下滑动/点击/鼠标滚轮，松手自动吸附到最近秒
  * 上下两端渐变淡出，移动端流畅
  * 可配置 min/max/step/height/unit/disabled
- 爆款视频 Step1「文案视频时长」替换原 Select 下拉：
  * 范围 15–30 秒，步长 1 秒
  * 默认值从 15 秒改为 20 秒
  * label 右侧实时紫色徽章显示「N秒」当前值
  * 底部提示「上下滑动选择 15–30 秒视频时长」
- CSS 新增 .vv-label-value 紫色小徽章样式
- 切换视频模型时仍按模型 max_duration 自动 clamp（seedance-2.5 支持 30s，其他 max=15 模型切回时自动落到 15s）

注：积分 UI 恢复（ENABLE_CREDIT_SYSTEM=true）已在 PR #2193 合入 develop，本 PR 不再包含。

apps/web/src/components/common/DurationWheelPicker/DurationWheelPicker.css

@@ -0,0 +1,110 @@
+/* DurationWheelPicker —— 浅色紫主题滚轮时长选择器 */
+.dw-picker {
+  position: relative;
+  width: 100%;
+  overflow: hidden;
+  border-radius: 10px;
+  background: #fafafe;
+  border: 1px solid #e5e7eb;
+  user-select: none;
+  -webkit-user-select: none;
+}
+
+.dw-picker-disabled {
+  opacity: 0.5;
+  pointer-events: none;
+}
+
+.dw-picker-list {
+  margin: 0;
+  padding: 0;
+  list-style: none;
+  height: 100%;
+  overflow-y: scroll;
+  scroll-snap-type: y mandatory;
+  -webkit-overflow-scrolling: touch;
+  scrollbar-width: none;
+}
+.dw-picker-list::-webkit-scrollbar {
+  display: none;
+}
+
+.dw-picker-item {
+  display: flex;
+  align-items: baseline;
+  justify-content: center;
+  gap: 4px;
+  scroll-snap-align: center;
+  cursor: pointer;
+  font-size: 20px;
+  color: #9ca3af;
+  font-weight: 400;
+  transition:
+    color 0.15s ease,
+    transform 0.15s ease,
+    font-weight 0.15s ease;
+}
+.dw-picker-item-val {
+  font-variant-numeric: tabular-nums;
+  font-size: 22px;
+}
+.dw-picker-item-unit {
+  font-size: 16px;
+  color: inherit;
+}
+
+.dw-picker-item-active {
+  color: #7c3aed;
+  font-weight: 600;
+  transform: scale(1.12);
+}
+.dw-picker-item-active .dw-picker-item-val {
+  font-size: 28px;
+}
+.dw-picker-item-active .dw-picker-item-unit {
+  font-size: 18px;
+}
+
+/* 中心选中条：浅紫背景 + 上下分隔线 */
+.dw-picker-mask {
+  position: absolute;
+  left: 8px;
+  right: 8px;
+  pointer-events: none;
+  background: #f5f0ff;
+  border-radius: 8px;
+  z-index: 1;
+}
+.dw-picker-mask::before,
+.dw-picker-mask::after {
+  content: "";
+  position: absolute;
+  left: 0;
+  right: 0;
+  height: 1px;
+  background: #d8c4ff;
+}
+.dw-picker-mask::before {
+  top: 0;
+}
+.dw-picker-mask::after {
+  bottom: 0;
+}
+
+/* 上下渐变淡出 */
+.dw-picker-fade {
+  position: absolute;
+  left: 0;
+  right: 0;
+  height: 40%;
+  pointer-events: none;
+  z-index: 2;
+}
+.dw-picker-fade-top {
+  top: 0;
+  background: linear-gradient(to bottom, #fafafe 30%, rgba(250, 250, 254, 0));
+}
+.dw-picker-fade-bottom {
+  bottom: 0;
+  background: linear-gradient(to top, #fafafe 30%, rgba(250, 250, 254, 0));
+}

apps/web/src/components/common/DurationWheelPicker/index.tsx

@@ -0,0 +1,157 @@
+/**
+ * DurationWheelPicker —— 竖屏滚轮式时长选择器
+ *
+ * 设计要点：
+ * - 原生 scroll + scroll-snap 模拟移动端滚轮 picker，无需额外依赖
+ * - 选中行有紫色背景高亮 + 放大加粗，视觉与爆款视频页紫白主题一致
+ * - 支持触摸 / 鼠标滚轮 / 点击跳转；滑动松手后吸附到最近项
+ * - 范围 15–30 秒，步长 1 秒
+ */
+import React, { useEffect, useRef, useState, useCallback } from "react"
+import "./DurationWheelPicker.css"
+
+export interface DurationWheelPickerProps {
+  /** 当前选中值（秒） */
+  value?: number
+  /** 最小值，默认 15 */
+  min?: number
+  /** 最大值，默认 30 */
+  max?: number
+  /** 步长，默认 1 */
+  step?: number
+  /** 单位文案，默认 "秒" */
+  unit?: string
+  /** 选择回调 */
+  onChange?: (value: number) => void
+  /** 容器高度，默认 200px（约 5 行可见） */
+  height?: number
+  /** 禁用 */
+  disabled?: boolean
+}
+
+const ITEM_HEIGHT = 40
+
+const DurationWheelPicker: React.FC<DurationWheelPickerProps> = ({
+  value = 20,
+  min = 15,
+  max = 30,
+  step = 1,
+  unit = "秒",
+  onChange,
+  height = 200,
+  disabled = false,
+}) => {
+  const options: number[] = []
+  for (let v = min; v <= max; v += step) options.push(v)
+
+  const listRef = useRef<HTMLUListElement>(null)
+  const [active, setActive] = useState<number>(value)
+  const isUserScrollingRef = useRef(false)
+  const scrollTimerRef = useRef<ReturnType<typeof setTimeout> | null>(null)
+
+  useEffect(() => {
+    if (isUserScrollingRef.current) return
+    if (value !== active) {
+      setActive(value)
+      scrollToValue(value, false)
+    }
+    // eslint-disable-next-line react-hooks/exhaustive-deps
+  }, [value])
+
+  useEffect(() => {
+    scrollToValue(active, false)
+    // eslint-disable-next-line react-hooks/exhaustive-deps
+  }, [])
+
+  const scrollToValue = useCallback(
+    (v: number, smooth = true) => {
+      const list = listRef.current
+      if (!list) return
+      const idx = options.indexOf(v)
+      if (idx < 0) return
+      const top = idx * ITEM_HEIGHT
+      list.scrollTo({ top, behavior: smooth ? "smooth" : "auto" })
+    },
+    [options],
+  )
+
+  const computeActiveFromScroll = useCallback(() => {
+    const list = listRef.current
+    if (!list) return
+    const idx = Math.round(list.scrollTop / ITEM_HEIGHT)
+    const clamped = Math.max(0, Math.min(options.length - 1, idx))
+    const v = options[clamped]
+    if (v !== active) {
+      setActive(v)
+      onChange?.(v)
+    }
+  }, [active, onChange, options])
+
+  const handleScroll = () => {
+    isUserScrollingRef.current = true
+    if (scrollTimerRef.current) clearTimeout(scrollTimerRef.current)
+    scrollTimerRef.current = setTimeout(() => {
+      const list = listRef.current
+      if (!list) return
+      const idx = Math.round(list.scrollTop / ITEM_HEIGHT)
+      const clamped = Math.max(0, Math.min(options.length - 1, idx))
+      const targetTop = clamped * ITEM_HEIGHT
+      if (Math.abs(list.scrollTop - targetTop) > 1) {
+        list.scrollTo({ top: targetTop, behavior: "smooth" })
+      }
+      computeActiveFromScroll()
+      isUserScrollingRef.current = false
+    }, 120)
+  }
+
+  const handleItemClick = (v: number) => {
+    if (disabled) return
+    setActive(v)
+    onChange?.(v)
+    scrollToValue(v, true)
+  }
+
+  const maskTop = height / 2 - ITEM_HEIGHT / 2
+
+  return (
+    <div
+      className={`dw-picker${disabled ? " dw-picker-disabled" : ""}`}
+      style={{ height }}
+      aria-label="视频时长选择"
+      aria-disabled={disabled}
+    >
+      <div className="dw-picker-mask" style={{ top: maskTop, height: ITEM_HEIGHT }} aria-hidden />
+      <div className="dw-picker-fade dw-picker-fade-top" aria-hidden />
+      <div className="dw-picker-fade dw-picker-fade-bottom" aria-hidden />
+
+      <ul
+        ref={listRef}
+        className="dw-picker-list"
+        onScroll={handleScroll}
+        style={{
+          paddingTop: height / 2 - ITEM_HEIGHT / 2,
+          paddingBottom: height / 2 - ITEM_HEIGHT / 2,
+        }}
+      >
+        {options.map((v) => {
+          const isActive = v === active
+          return (
+            <li
+              key={v}
+              className={`dw-picker-item${isActive ? " dw-picker-item-active" : ""}`}
+              style={{ height: ITEM_HEIGHT, lineHeight: `${ITEM_HEIGHT}px` }}
+              onClick={() => handleItemClick(v)}
+              aria-selected={isActive}
+              role="option"
+            >
+              <span className="dw-picker-item-val">{v}</span>
+              <span className="dw-picker-item-unit">{unit}</span>
+            </li>
+          )
+        })}
+      </ul>
+    </div>
+  )
+}
+
+export default DurationWheelPicker

apps/web/src/pages/viral-video/ViralVideoPage.css

@@ -393,6 +393,15 @@
   margin-bottom: 6px;
   font-weight: 500;
 }
+.vv-label-value {
+  margin-left: 8px;
+  padding: 2px 8px;
+  border-radius: 6px;
+  background: #f5f0ff;
+  color: #7c3aed;
+  font-size: 12px;
+  font-weight: 600;
+}
 .vv-label-optional {
   color: #9ca3af;
   font-weight: 400;

apps/web/src/pages/viral-video/ViralVideoPage.tsx

@@ -30,6 +30,7 @@ import { uploadAssetDirect, getAssetLibraries, getAssetsByKind, type AssetItem }
 import { fetchPresetVoices } from "@/api/voices"
 import { getVoiceClones, getVoiceClonePreview } from "@/api/voice-clone"
 import type { VoiceClone } from "@/api/voice-clone"
+import DurationWheelPicker from "@/components/common/DurationWheelPicker"
 import {
   FUSION_LEVELS,
   STYLE_STRENGTHS,
@@ -218,7 +219,6 @@ const PURPOSES = [
   "悬念短剧",
   "情绪短片",
 ]
-const DURATIONS = [15, 20, 30, 45, 60]
 const RATIOS = [
   { v: "9:16", label: "9:16 竖屏（抖音/视频号）" },
   { v: "16:9", label: "16:9 横屏（B站/YouTube）" },
@@ -437,7 +437,7 @@ const emptyTask = (id: string, title: string): TabTask => ({
   language: "中文(普通话)",
   viralStructure: STRUCTURES[0],
   marketingPurpose: "",
-  duration: 15,
+  duration: 20,
   persona: "",
   videoRatio: "9:16",
   videoModel: "seedance-2.5",
@@ -2432,14 +2432,19 @@ const ViralVideoPage: React.FC = () => {
                   />
                 </div>
                 <div className="vv-form-row" style={{ gridColumn: "1 / -1" }}>
-                  <label className="vv-label">文案视频时长</label>
-                  <Select
-                    className="vv-select"
-                    style={{ width: "100%" }}
+                  <label className="vv-label">
+                    文案视频时长
+                    <span className="vv-label-value">{task.duration}秒</span>
+                  </label>
+                  <DurationWheelPicker
                     value={task.duration}
-                    onChange={(v) => setTask({ duration: v })}
-                    options={DURATIONS.map((n) => ({ value: n, label: `${n}秒` }))}
+                    min={15}
+                    max={30}
+                    step={1}
+                    height={200}
+                    onChange={(v: number) => setTask({ duration: v })}
                   />
+                  <div className="vv-form-hint">上下滑动选择 15–30 秒视频时长</div>
                 </div>
               </div>